The present invention relates to an onboard avionic system for communication between an aircraft and the ground and a method for managing a radio channel of such a system.
The technical field of the present invention is that of data communications between aircraft in flight and ground stations, such as stations for air traffic control, stations for airline companies, stations for aircraft maintenance, etc. FIG. 1 shows an air data communications system to which the present invention applies. This communications system comprises a ground system 10 for transmitting data and, in each aircraft, an avionic communication system 20.
The ground communications system 10 comprises ground stations 2, 3 and 4 providing wireless communications with the avionic communication systems 20 of aircraft 5. The ground station 2 provides communications in a frequency band called VHF, the ground station 3 provides communications in a frequency band called HF and the ground station 4 provides communications relayed by a satellite 6. The communications system 10 also comprises ground stations 7, 8 and 9 respectively for providing, by way of example, air traffic control services, airline company services and maintenance services. The ground stations 7, 8 and 9 and the ground stations 2, 3 and 4 exchange data between each other via a network 1.
FIG. 2 shows an avionic communications system 20 present in each aircraft 5. It comprises a service unit 21 to which are connected different equipment 22, 23, 24, 251 to 25N. The equipment 22, 23, 24 are constituted by equipment which between them form a man-machine interface for the pilots of the aircraft in question and are, conventionally, a printer 22 for printing messages transmitted to the aircraft, a keyboard 23 for inputting messages intended for a ground station and an alarm 24. The equipment 251 to 25N are devices for measuring or detecting flight conditions of the aircraft in question. Radio communications units 26, 27 and 28 are also connected to the service unit 21. The radio communications unit 26 provides communications in a frequency band called VHF, the radio communications unit 27 provides communications in a band called HF and the radio communications unit 28 provides satellite communications. The service unit 21 is, for example, a router which allows the exchange of data between the equipment 22, 23, 24, 251 to 25N of the aircraft in question and the radio communications units 26, 27 and 28 and beyond, with the ground stations 2, 3 and 4 and furthermore, via the network 1, with the ground stations 7, 8 and 9.
Among the air data communication systems can be mentioned the networks called ATN (Aeronautical Telecommunication Network) or the network called ACARS (Aircraft Communication Addressing and Reporting System).
Digital data are thus exchanged between an aircraft and a ground station and this can be either at the initiative of the pilots of the aircraft in question or at the initiative of a ground station or automatically at regular time intervals. The digital data can relate to messages about flight conditions of the aircraft in question sent by the aircraft to a control tower or vice-versa, information messages to the pilots or to the air traffic controllers, or to maintenance workshops or to the airline company to which the aircraft belongs, etc.
With the increase in the number of flights, the problem of congestion of radio resources which may not be available at the moment of exchanging data arises. If the VHF frequency band which extends from 118 MHz to 137 MHz is considered, the use of a single frequency contributes to this congestion, notably in certain flight zones more congested than others.